The Bureau of Meteorology in Beijing and Foshan began constructing an X-band dual-polarization radar networks to enhance their ability to elaborate nowcasting. However, in the following two years of flood season observation, it is found that there are still a series of problems in X-band dual-polarization radar, and its data quality that could be improved largely. The article uses the characteristics of polarization parameters that uniformed in nature and slowly changed with time and space in the process of weak rainfall and selects the observation data of weak precipitation process in Beijing and Foshan. Through the method of accumulating in radial or azimuth by taking a long-term observation, this paper analyzes the accuracy of polarization parameter measurement that affected by the ground, lightning rod, rotation and pitching joints and puts forward to the corresponding quality control method. The following conclusions are drawn:(1) different reflectivity factor (ZDR), correction coefficient (ρhv) and differential propagation phase (ΦDP) are more sensitive to the ground objects than horizontal polarization reflectivity factor (Z), where ρhv is less than 0.85, ZDR lower than -1 dB, and a threshold of 0.9 is set according to the difference of ρHV between rainfall and ground objects. The ρhv can be accumulated for a long time to identify the echo of ground object effectively. (2) The azimuth and amplitude of each lightning rod's influence on the dual polarization parameters are approximately the same. In the ±15° azimuth range centered on the lightning rod, the ZDR increases by approximately 0.4 dB to 1.5 dB, the ρhv lowers to 0.01 or less, and the Z decreases by nearly 1 to 2 dBZ, and in which these parameters will reach the extremum. Through the statistical correction based on the above azimuth, the effect of lightning protection on dual polarization parameters can be better removed. (3) The abnormality of the rotary joints will cause the ZDR to change unevenly in the horizontal direction, while the exception of pitching joint will cause the ZDR to have a large gap between the high and low elevation angles. The ZDR variation curve of the elevation angle of each layer will be obtained through the accumulation of the ZDR along the azimuth for a period of time, which can achieve ZDR error calibration. Through the test, the quality control method proposed in this paper can effectively improve the data quality of X-band dual-polarization radar and provides support for its further promotion in operation.
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